Short-term associations between outdoor air pollution and visits to accident and emergency departments in London for respiratory complaints

Many epidemiological studies have shown positive short-term associations be tween health and current levels of outdoor air pollution, The aim of this s tudy was to investigate the association between air pollution and the numbe r of visits to accident and emergency (A&E) departments in London for respi ratory complaints. A&E visits include the less severe cases of acute respir atory disease and are unrestricted by bed availability. Daily counts of visits to 12 London A&E departments for asthma, other respi ratory complaints, and both combined for a number of age groups were constr ucted from manual registers of visits for the period 1992-1994, A Poisson r egression allowing for seasonal patterns, meteorological conditions and inf luenza epidemics was used to assess the associations between the number of visits and six pollutants: nitrogen dioxide, ozone, sulphur dioxide, carbon monoxide, and particles measured as black smoke (BS) and particles with a median aerodynamic diameter of <10 mu m(PM10), After making an allowance for the multiplicity of tests, there remained str ong associations between visits for all respiratory complaints and increase s in SO2: a 2.8% (95% confidence interval (CI) 0.7-4.9) increase in the num ber of visits for a 18 mu g m(-3) increase (10th-90th percentile range) and a 3.0% (95% CI0.8-5.2) increase for a 31 pg ms increase in PM10, There wer e also significant associations between visits for asthma and SO2, NO2 and PM10, No significant associations between O-3 and any of the respiratory co mplaints investigated were found. Because of the strong correlation between pollutants, it was difficult to identify a single pollutant responsible fo r the associations found in the analyses. This study suggests that the levels of air pollution currently experienced in London are linked to short-term increases in the number of people visiti ng accident and emergency departments with respiratory complaints.